In my use case I only wanted to see if a Bluetooth headset is connected for a VoIP app. The following solution worked for me:
public static boolean isBluetoothHeadsetConnected() {
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
return mBluetoothAdapter != null && mBluetoothAdapter.isEnabled()
&& mBluetoothAdapter.getProfileConnectionState(BluetoothHeadset.HEADSET) == BluetoothHeadset.STATE_CONNECTED;
}
Of course you'll need the Bluetooth permission:
<uses-permission android:name="android.permission.BLUETOOTH" />